In order to solve the problem that the traditional variational level set segmentation algorithm is poor in segmenting uneven gray images and sensitive to the initial contours, we propose an adaptive active contour model based on local and global information coupling. By adjusting the proportion of local region fitting energy and global region fitting energy by weight function, a weight function which is adaptively updated with the evolution of the contour is given. Experiments results in synthetic images, real images and natural images show that the algorithm is robust to noise and insensitive to the initial position of the contours.